Digital Modes
PACTOR is an FSK mode. It is designed with a combination of packet and Amtor Techniques. It is a very popular digital mode on amateur HF today. This mode is a major advancement over AMTOR, with its 200 baud operating rate, Huffman compression technique and true binary data transfer capability.
PACTOR-II is a robust PSK mode which operates well under varying conditions. It uses strong logic, automatic frequency tracking; it is DSP based and as much as 8 times faster then Pactor. Both PACTOR and PACTOR-2 use the same protocol handshake, making the modes compatible.
PACTOR-III is a proprietary mode used for message and traffic handling over an HF radio circuit. Use of Pactor-III protocol is limited for US hams and some other countries due to the wide bandwidth of the Pactor-III signal. Presently digital signals that occupy the bandwidth of PCT-III are restricted to a few sub bands.
G-TOR (Golay -TOR) is an FSK mode that offers a fast transfer rate compared to Pactor. It incorporates a data inter-leaving system that assists in minimizing the effects of atmospheric noise and has the ability to fix garbled data. G-tor tries to perform all transmissions at 300 baud but drops to 200 baud if difficulties are encountered and finally to 100 baud.
CLOVER> is a PSK mode which provides a full duplex simulation. It is well suited for HF operation, however, there are differences between CLOVER modems. The original modem was named CLOVER-I, the latest DSP based modem is named CLOVER-II. Clovers key characteristics are band-width efficiency with high error-corrected data rates. Clover adapts to conditions by constantly monitoring the received signal. Based on this monitoring, Clover determines the best modulation scheme to use.
RTTY or "Radio Teletype" is an FSK mode that has been in use longer than any other digital mode (except for morse code). RTTY is a very simple technique which uses a five-bit code to represent all the letters of the alphabet, the numbers, some punctuation and some control characters. At 45 baud (typically) each bit is 1/45.45 seconds long, or 22 ms and corresponds to a typing speed of 60 WPM. There is no error correction provided in RTTY; noise and interference can have a seriously detrimental effect. Despite it's relative disadvantages, RTTY is still popular with die-hard operators.
PSK31 is the first new digital mode to find popularity on HF bands
in many years. It combines the advantages of a simple variable length
text code with a narrow bandwidth phase-shift keying (PSK) signal using
DSP techniques. This mode is designed for "real time" keyboard
operation and at a 31 baud rate is only fast enough to keep up with the
typical amateur typist. PSK31 enjoys great popularity on the HF bands
today and is presently the standard for live keyboard communications.
Most of the ASCII characters are supported. A second version having
four (quad) phase shifts (QPSK) is available that provides Forward
Error Correction (FEC) at the cost of reduced Signal to Noise ratio.
PSK31 home page
HF PACKET radio is a FSK mode that is an adaption of the very popular Packet radio used on VHF FM ham radio. Although the HF version of Packet Radio has a much reduced bandwidth due to the noise levels associated with HF operation, it maintains the same protocols and ability to "node" many stations on one frequency. Even with the reduced bandwidth (300 baud rate), this mode is unreliable for general HF ham communications and is mainly used to pass routine traffic and data between areas where VHF repeaters maybe lacking.
MFSK Information
MultiPSK supported modes
Digital Mode Info
- Frequency-shift keying
- FSK shifts between two known states. FSK is sent by either shifting a carrier frequency (F1B) or modulating SSB with two shifting audio tones (AFSK).
- Phase-shift keying
- PSK changes PHASE of a signal against some reference. When sending PSK, a complex audio waveform is transmitted by SSB. Frequency stability is critical for PSK.
- DSP (Digital Signal Processing)
- Techniques using high speed processing to convert audio into digital coding, so that a program can manipulate the coded audio in ways not possible with traditional hardware filters.
- MFSK (Multi Frequency Shift Keying)
- MFSK is a technique for transmitting digital data using multiple tones, extending the RTTY two-tone technique to many tones, usually, but not always, one tone at a time